How does the crassulacean acid metabolism (CAM) pathway in desert plants reduce transpiration?

Correct answer: It opens the stomata mainly at night, when evaporative demand is lower

Correct answer: B. CAM plants separate carbon dioxide uptake from much of the daytime carbon-fixation activity. Their stomata generally open at night, when temperature is lower and the difference in water vapour concentration between the leaf and air is often smaller. Carbon dioxide is taken up and fixed into organic acids, commonly malate, which is stored in vacuoles. During the hot, dry daytime, stomata remain mostly closed; the stored acid releases carbon dioxide inside the leaf for photosynthesis. Closing stomata during the period of greatest evaporative demand greatly reduces water loss, although it does not eliminate transpiration completely. A is false because stomata remain functional, C would increase water loss, and D is unrelated to the CAM mechanism. Memory cue: CAM takes carbon dioxide at night and saves water by closing stomata in daytime.